问题
When I try the firstOrCreate() on a relationship of another model, it does not work:
Client::find($id)->users()->firstOrCreate(array('email' => $email));
This returns an error saying
Call to undefined method Illuminate\Database\Query\Builder::firstOrCreate()
Running this directly on the model User will work though.
回答1:
This won't work, you have to do it manually/directly using User model because users() should return a collection object
This is correct, the users() function does not return a (new, empty or created) User model, it returns a collection object.
It's also documented http://laravel.com/docs/5.1/eloquent-relationships#inserting-related-models if you use the laravel relations than it should work.
You are misinterpreting that document. The relationship object has a create() method and a save() method, however the relationship object is not a full model object. To get all of the functionality of a full User model object (such as firstOrCreate()) then you have to call them on the model object.
So, for example, this code should work:
$user = User::firstOrNew(array('email' => $email));
Client::find($id)->users()->save($user);
Note that it should be OK to save the $user object here directly from the Client model's relationship, even though it may already exist here, it should just update the client_id field on the $user object when you do so.
来源：https://stackoverflow.com/questions/23965615/laravel-eloquent-firstorcreate-on-a-relationship